This application relates to a multi-passage heater assembly. More particularly, the application relates to a multi-passage heater assembly suitable for use with, for example, a gas dynamic cold spray gun.
Portable gas dynamic spray guns are being developed to widen their application and reduce the cost of using cold spray technology. Low-pressure cold spray systems are used for spraying powdered material at supersonic velocities. The low-pressure carrier gas is supplied to the spray gun at typically less than 10 bar (150 psi). The carrier gas passes through a heater assembly, which heats the carrier gas to reduce its density. The heated gas then flows through a venturi throat and is accelerated. Powdered material is then introduced into the gas jet and is expelled at a supersonic velocity towards a substrate. The powdered material typically includes a single constituent abrasive, metal, metal alloy or a blend of such materials. The powdered material can be used to prepare (clean or abrade) the surface or deposit a coating onto the substrate.
It is desirable to commercialize portable gas dynamic spray units, which has not been done very successfully. Prior art cold spray guns are rather heavy and can pose safety issues to the user due to the high operating temperature of the heater assembly, which may be between 400-650° C. during use. Moreover, packaging the cold spray gun components in a portable size that is also durable can be difficult. For example, the heater assembly in some cold spray guns is susceptible to breakage and electrical shorts due to rough handling. Other heater assemblies, which are rather heavy and not adapted to cold spray technology, generate heat in such a way that would expose the user to very high temperatures.
What is needed is a gas dynamic spray unit more suitable for commercialization.